Process of making a colloidal suspension of phosphates



June 14, 1960 J. BLINKA PROCESS OF MAKING A COLLOIDAL SUSPENSION OF PHOSPHATES Filed Oct. 5, 1956 I #J 4 s I TEMPERATURE F INVENTOR.

ATTORNEYS.

' sion.

PROCESS OF MAKING A COLLOIDAL SUSPENSION OF PHOSPHATES & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Oct. 5, 1956, Ser. No. 614,293

\ 10 Claims. (Cl. 252-309) This invention relates to a method of making colloidal suspensions of certain phosphates. These phosphates are the water-soluble, ortho-, pyro-, and tripolyphosphates which are useful as detergency builders with soaps and synthetic detergents.

In the prior art, fine particles of builders were producted by one of two methods. The most used method was mechanical disintegration-the large particles were ground to smaller particles in a ball mill, a roller mill, or a colloid mill. These methods are power consuming, and if capable of producing particles of less than microns in size do so only at the expense of large amounts of power. The other method of producing fine particles is to dissolve the batch of material to be rendered into fine particles in a solvent for the material, and then pour this solution into a liquid in which the material is insoluble, thereby precipitating fine particles. This method has serious disadvantages. It will be readily perceived that the liquid into which the solution is poured must be there in large quantity with reference to the solution, so as to negate the solvent qualities of the solvent. The two liquids must be miscible, otherwise colloidal phosphates will not form. Rarely will the second liquid be the one in which the dispersion is desired. It the second liquid is the desirable one, there is the problem of driving oii the original solvent. If the proper liquids are selected, very fine particles may be made in this manner but it is an expensive and time consuming one.

I have discovered that fine dispersions may be prepared by a simple process which apparently depends upon the fact that the hydrates of the sodium and potassium salts of ortho-, pyro-, and tripolyphosphate are more soluble in glycerol, glycois, and l-octanol than are the anhydrous forms of these salts. When an excess of any of these hydrates in commercially ground form is agitated in these hydroxylated materials the hydrate dissolves in small amounts, say, from 2% to 2%, The dissolved hydrate may then be dehydrated by the water absorbing qualities of these hydroxylated solvents and by the suitable control of vacuum and heat upon the suspension. The dehydrated phosphate is precipitated in fine particle size, about 0.1 micron. By continuing the vacuum and heat, at least 75% of the phosphate can be dehydrated and precipitated in the fine form. If the final suspension is to be retained in the dehydrating hydroxylated liquid as a vehicle for its use, a detergent may be dissolved at any point where foaming is not a problem, and silicate of soda, suds boosters, and other additives added to the disper- Mechanically produced fine particles of inorganic builder may be added within limits, and will be prevented from settling by the fine dispersion of dehydrated phosphate. These added builders may be of commercial grind, about 25 microns in size.

' If the dehydrating and colloiding of the phosphate is carried out in a liquid which is not desirable in the final product, the dispersion may be centrifuged from the dehydrating liquid. It may then be suspended in the desired liquid or it may be added to a bar, flaked, or granular 2,940,938 Patented June 14, 1960 detergent. In dry or concentrated paste form the colloidal anhydrous phosphates of the invention are especially useful in making built milled bars and flakes of soap and/ or synthetic detergent.

Equipment suitable for carrying out the process of my invention is shown in Figure 1 in which:

=1. Denotes the premix tank An agitator therein A drop line from the premix tank A pump for delivering through the delivery line A delivery line A valve in the delivery line A recirculating pump A heat exchanger fitted with steam and condensate connections, and with cooling water connectors, not shown 9. A delivery line to the reactor 10. A reactor in which the phosphate dehydration is carried out 11. A nozzle so placed as to secure agitation in the reactor 12. A recirculation line from the reactor to the inlet of a recirculation pump 13. A vapor line from the reactor 14. A condenser in the vapor line 15. A drop line from the condenser 16. A valve in the drop line 17. A steam ejector 18. A steam line to the ejector 19. A barometric condenser 20. A waterline to the condenser 21. A take-off line 22. A valve in the take-off line In operation the octanol, glycol, glycerin, glycolglycerin or mixtures of any of these is placed in premix tank '1. For convenience the hydroxylated liquid portion will be called the vehicle. The hydrated phosphate is then added and mixed for some time as hereinafter explained. In batch operation, the mix is transperred by pump 4t0 reactor 10. The charge is cycled through line 12 and pump 7 and delivered through nozzle 11 into the reactor 10. The recirculation pump-7 is used to recycle the mix, thus agitating it. Heating or cooling to maintain temperature is secured by regulating the flow of steam or water through heat exchanger 8. If desired, a vacuum is imposed upon the reactor by operating the ejector 17, by turn-on steam at P8 and condensing water at 20.

The condenser 14 is not an essential part of the operation, but in operations carried out at atmospheric pressure it prevents water vapor from being discharged into the building. However the condenser is a convenience even in vacuum operation, 'as the amount of water condensed is an indication of the rate of dehydration taking Example I This was a batch operation as described above. Equal weights of Na P O -10H O and ethylene glycol were charged into the premix tank and the mixer run for about 40 minutes. This mixing is desirable so as to thoroughly wet all of the particles and break up agglomerates which might persist throughout the dehydration. The mix was exchanger which was regulated to hold the top tempera-- ture of the reaction mix at 154 F. After 210 minutes, the steam was shut off the heat exchanger and the mix dropped from the reactor through line 21. The 210 minutes probably was unnecessarily long, but this was the first processing of this material, herice it was heated under vacuum for a time that would insure dehydration. The pyrophosphate was converted to the colloidal form.

For a relatively rapid method of determining the extent of the dehydration of the phosphate, a moisture method is used. This is modification of Oflicial Method Ea-8-50 of the American Oil Chemists Society and determines the total water in the dehydrated mix. A weighed portion of: the mix is taken and diluted with anhydrous methanol toma specific volume. After thorough agitation for 15 minutes the sample is allowed to settle. A portion of the supernatant liquor is pipetted into a 125 ml. Erlenmeyer flask containing an excess of Fischer reagent. With moderate agitation the residual excess is backtitrated with methanol water standard, and the total water content of the original sample is calculated. The free water is determined by the A.O.C.S. Ofiicial method, not modified, on a portion of the preparation which is pipetted from the supernatant liquid of an 80% isobutanol-20% methanol dispersion of the sample. The free water divided by the total water is a measure of the extent of the dehydration that has been accomplished.

Example 11 40 parts of sodium tripolyphosphate, 'Na P O '6H O was suspended in a vehicle consisting of 30 parts of propylene glycol and 10 parts of glycerin. 'This was processed by the batch method previously described. The absolute pressure was 20 millimeters of mercury at the start and was decreased to 13 millimeters of mercury at the finish. The batch was charged into the reactor at 80F. and was cycled through the heat exchanger until the temperature reached 182 F. This temperature was maintained until the batch had been processed for 70 minutes. This suspension had good stability upon standing. The X-ray diffraction pattern showed the phosphate to be'Form II.

Example III 135' parts of sodium tripolyphosphate, Na P O -6H 0,

were suspended in 94 parts of propylene glycol and 31 partsof glycerin. This was processed by the continuous method, at 150 F. and 20 millimeters of mercury pressure. The rate of driving off water becomes the control in-this method. This is followed by the water collected from the condenser 14. 3 parts of water per minute were driven ofi in this example. This corresponds to 10.2 parts of anhydrous sodium tripolyphosphate being formed/min. Since the original mix at 135 parts of Na P O -6H O contained the equivalent of 104 parts of Na P O in the 125 parts of vehicle, a simple calculation will show that to withdraw each 10.2 parts of anhydrous tripolyphosphate from the take-01f line (21 in Fig. 1) it will be necessary to withdraw 10.2=12.3 parts of vehicle with this 10.2 parts of phosphate or a total of 22.5 parts of the dehydrated suspension.

This suspension did not. settle, and had a total moisture of less than 1%.

Example IV This was a batch run in different equipment than that shown in Figure 1. A simple jacketed vessel open to the atmosphere was used. Hot water was circulated through the jacket to maintain the temperature. Th (Q l The temperature was allowed'to rise to;150 F. and main- Moderate sparging Was maintained. throughout the run. This had two effects, agitation to sus equipped with a sparger at the bottom connected to the compressed air line. 13 pounds of glycerin were added to the vessel and hot water circulated through the jacket. There was then added, with the spar'ger turned on to give a moderate agitation, 75 pounds of sodiumtripolyphosphate Na P O tained at that point.

Example V On 100 grams of anhydrous potassium tripolyphosphate, there'was sprayed 10 grams of water. There is very littleinformation about the hydrates of potassium tripolyphosphate, but the amounts of phosphate and water used would correspond closely to K P O -2H O. This moistened potassium tripolyphosphate has an X-ray diffraction pattern like a hydrate and behaves as the known crystalline hydrates behave in the process of this invention, and it will be therefore described as a crystalline hydrate.

50 grams of the hydrated potassium phosphate presumably containing of the original grams of anhydrous potassium phosphate, or 45.5 grams, was stirred into 100 grams of ethylene glycol.- The absolute pressure was reduced to 20 millimeters of mercury and the suspension heated to 180 F. A fine suspension of a mixture of colloidal and noncolloidal potassium tripolyphos-' phate resulted from this treatment. a

The following examples illustrate how the invention can be carried out with other materials. In each case the phosphate that is used as the starting material, which if initially anhydrous can first be hydrated by spraying the powdered phosphate with water as in Example V,'is thoroughly stirred with about an equal weight of vehicle and this mixture is then subjected to subatmospheric pressure at a temperature of about F., with continuing mechanical agitation, until the phosphate is for the most part converted to an anhydrous colloidal condition.

The conditions under which the hydrate Na5P3010 may be converted to the anhydrous colloidal N-a P 0 may be understood by reference to Figure 2. The values were arrived at by placing an excess of Na P O -6H 0 in the vehicle and maintaining the temperature listed until no further increase in water content of the vehicle occurred.

The curves show that even at low temperatures the .glycols and glycerin absorb moisture from the hexahydrate. The process taking place, I believe, is first the dissolving of the hexahydrate in the vehicle, secondthe absorption of the water from the dissolved hexahydrate by the vehicle and third the precipitation of the anhydrous tripolyphosphate. X-ray diflraction patterns show this colloidal precipitate to be principally Form II sodium tripolyphosphate. That anhydrous tripolyphosphate is thus produced is a most unexpected result. In the chap 52 pounds of propylene glycol and for on Phosphoric Acids and Phosphates in the Encyclopedia of Chemical Technology, vol. 10, published by the Interscience Encyclopedia Inc, 1952, I. R. Van Wazer states on page 413;

Once the anhydrous salt has been hydrated, the water cannot be removed without breaking down the molecule. Even when dehydration is carried out under the most gentle conditions, a mixture of pyroand orthophosphate always results.

The reference above, starting on page 413 and continuing on page 414, refers to Forms I and II tripolyphosphate.

The amount of the various forms inthe colloidal phosphate produced by dehydration of normal sodium tripolyphosphate in the vehicles of this invention is typified by the following results:

Vehicles causing'more than 20% of the anhydrous phosphate to be converted to forms other than tripolyphosphate should preferably not be used.

, At room temperature and atmospheric pressure the process goes only as far as indicated by the curves. The vehicle absorbs around 2.5% to 5% of water and then the process stops, probably because the vehicle is satu-- rated with respect to Na P O -6H O and water. The process can be carried further by removing the water from the hydrated phosphate dissolved in the vehicle. This can be accomplished by heat or vacuum or both. Example IV shows how heating with an air scavenge, but no vacuum, will carry the process to conclusion, although it takes a long time.

For use in compositions where anionic synthetic detergents are dissolved in the vehicle, the solubilizing power of the vehicle becomes important. Glycerinepropylene glycol mixtures are effective, about 10 to 50% glycerin, the remainder propylene glycol, is preferred. U.S. Letters Patent 2,864,770, issued December 16, 1958, describes detergent compositions in which the colloidal phosphates of the present invention are highly efiective.

It will be noted that the curves flatten out around 140 F. The preferred temperatures are from about 140 F. to about 180 F. 'The vacuum used most frequently is that corresponding to an absolute pressure of millimeters of mercury, not because there is any special advantage at that pressure but because it is as low as can be achieved without special equipment. Obviously any vacuum may be used.

It is desirable to mix the hydrate in the vehicle without heat or vacuum for a period to wet the particles with the vehicle and break up aggregates. This period of agitation should be from about 30 to about 60 minutes.

The upper limit of the percent of crystalline hydrates in the mixture is set by the condition that it must be stirrable. About 65 parts of crystalline hydrate to 35 parts of vehicle is about as high in solids as can be handled. The lower limit is that some crystalline hydrate be present.

It is undesirable to push the dehydration after agitation at a rate much greater than that achieved with a 160 F. temperature at 20 millimeters of mercury absolute pressure. It appears that such rapid dehydration dehydrates and decomposes (or hydrolyzes) some of the undissolved hydrate. This, of course, does not lead to a change in particle size in the portion which is dehydrated without dissolving.

Among the various monohydric alcohols tested for suitable vehicles, l-octanol is the only one capable of being used by itself to produce a colloidal phosphate by the method of this invention. Other monohydric alcohols, such as dodecanol, may be used along with a major proportion of glycols, however.

Other glycols, in addition to the ethylene glycol and propylene glycol shown in the examples are usable in this process. Butylene glycol and trimethylene glycol (isomeric with propylene glycol) will function to produce colloidal phosphates in the manner of this invention. The glycols above 4 carbon atoms are not good solvents for the hydrated:phosphates, hence the glycols usable are those described as saturated hydrocarbons of 2 to 4 carbon atoms, two of the carbons having hydroxyl constituents. 7

The glycols used and the l-octanol have vapor pressures, in the range of temperature use, of less than onefiftieth of that of water, thus there is no serious problem of volatilization of the vehicle, the water coming 01f almost in pure form.

Having thus described my invention, what I claim is:

1. A process of continuously removing the water of crystallization from hydrated phosphates comprising mixing crystalline hydrated phosphates with a vehicle selected from the group consisting of glycols of 2 to 4 carbon atoms, glycerine, l-octanol and mixtures thereof, said vehicle being at least 35% by weight of the mixture, continuously feeding said mixture to a reaction zone wherein said mixture is maintained at a temperature in the range from about 70 to about 180 F., under an absolute pressure ranging from about 4 mm. of mercury to atmospheric pressure and sufficient to allow evaporation of Water from the vehicle substantially as rapidly as the said vehicle absorbs water of crystallization from the crystalline hydrated phosphate, whereby said crystalline hydrated phosphate is dehydrated, and continuously withdrawing the phosphate-vehicle mixture from the reaction zone.

2. A process for removing the water of crystallization from crystalline hydrated tripolyphosphates which comprises suspending the crystalline hydrated tripolyphosphate in a vehicle having an affinity for water and selected from the group consisting of glycols of 2 to 4 carbon atoms, glycerine, and l-octanol, and mixtures thereof, effecting saturation of the vehicle with respect to said crystalline hydrated phosphate, maintaining the temperature of the suspension within the range from about 70 F. to about 180 F. while maintaining said suspension at an absolute pressure ranging from 4 millimeters to atmospheric pressure whereby a portion of the hydrated phosphate is dissolved in the vehicle, is rendered insoluble in the vehicle by removal of the water of crystallization of the phosphate and is precipitated as colloidal particles, thereby allowing successive portions of said crystalline hydrated tripolyphosphate to be dissolved, to be dispossessed of water of crystallization and to be precipitated, at least of the crystalline hydrated tripolyphosphate being converted to anhydrous phosphates comprising at least 80% tripolyphosphate.

3. The process of making a colloidal suspension of phosphates which comprises suspending a crystalline hydrated phosphate selected from the group consisting of hydrated trisodium orthophosphate, hydrated 'tr-ipotassium orthophosphate, hydrated sodium pyrophosphate, hydrated potassium pyrophosphate, hydrated sodium tripolyphosphate, hydrated potassium tripolyphosphate, and mixtures thereof, in a vehicle having an afiinity for water and selected from the group consisting of (1) a glycol of 2 to 4 carbon atoms, (2) glycerin, and (3) l-octanol, and mixtures thereof, eifecting saturation of the vehicle with respect to said hydrated phosphate by agitating the suspension, and removing water vapor from the suspension while maintaining the temperature of the suspension within the range of about 70 F. to about R, whereby successive portions of said hydrated phosphate are dissolved, rendered insoluble in the vehicle by removal of the water of crystallization of the phosphate and precipitated 7. as colloidal particles; without substantial decomposition and loss of the chemical identity 'fthe basic phosphate.

4. The process of claimilxriniwhich the rem'oval of watertvapoi'. is continu'ediuntii"atjleast 7'5%-fof the hydrated phosphate is dehydrated and precipitated in colloidalform. r g.

5. The process of claim 3 wherein the vehicle is eth ylene glycol. -6. The; process of ;claim 3 wherein thevehicle is glyceriner 1 x e 7. The process of' claim 3, in "which the phosphate suspended issodium tripolyphosphate with six molecules of water of hydration. e 8. The process 'of claim 7,in which the vehicle is a mixture of glycerin andpropylene glycol, said mixture being employed in the gratio of from 0.1:part to 1 part of glycerine to 1 pant-of propylene glycol. 1

9. The process of making a colloidal suspension of phosphatefwhich comprises suspending a crystalline hydrated phosphate selected fromthe group consisting of hydrated :trisodium orthophosphate, hydrated tripotassiuni orthophospha-te, hydrated sodium pyrophosphate, hydrated potassium pyrophosphate, hydrated sodium tripolyphosphate, hydrated potassium tripolyphosphatef, and mixtures thereofin ethyleneglycol, effecting satura; tion of the ethylene glycol wtih respect to said hydrated phosphate by agitating the suspension, and maintaining the temperature of the suspension within the range from about 70 to about 180 F., until no further-increase in the water content of the ethylene glycol occurs, whereby a portion of the hydrated phosphate is dissolved in the vehiele,iisdispossessedof water of crystallization-and isprecipit'ated as colloidal particles, the said colloidal particles ma ntainingther m n n hy atedrho pha e in suspension in the vehicle. j V 10. The process of making a colloi al'suspension' of phosphate which comprises suspending 'a crystalline hydrated phosphate selected from the group consis-ting of hydrated trisodium orthophosphate, hydrated tn'potassium orthophosphate, hydrated sodium pyrophosphate, hydrated potassium pyrophosphate, hydrated sodium tripolyphosphate, hydrated potassium tripolyphosphate, and mixtures thereof in glycerine, effecting saturation of the glycerine'with respect-to said hydrated phosphate by agi tating the suspension, and maintaining the temperature of the suspension within therange from about -F. to about -F., until no further increase inthe'water content of the glycerine occurs, whereby a portion of the hydrated phosphate is dissolved in the vehicle, i's dispossessed of its water of crystallization and is precipitated as colloidal particles, the said colloidal particles maintaining the remaining hydrated phosphate in suspension in the vehicle.

References Cited in the file of this paten t UNITED STATES PATENTS 1,922,006 Hoessle Aug. 6, 1933 2,277,854 Lecoq Mar. 31,- 1942 2,296,716 Jelen Sept. 22, 1942 2,368,560 Minich Ian. 30', 1945 

3. THE PROCESS OF MAKING A COLLOIDAL SUSPENSION OF PHOSPHATES WHICH COMPRISES SUSPENDING A CRYSTALLINE HYDRATED PHOSPHATE SELECTED FROM THE GROUP CONSISTING OF HYDRATED TRISODIUM ORTHOPHOSPHATE, HYDRATED TRIPOTASSIUM ORTHOPHOSPHATE, HYDRATED SODIUM PYROPHOSPHATE, HYDRATED POTASSIUM PYROPHOSPHATE, HYDRATED SODIUM TRIPOLYPHOSPHATE, HYDRATED POTASSIUM TRIPOLYPHOSPHATE, AND MIXTURES THEREOF, IN A VEHICLE HAVING AN AFFINITY FOR WATER AND SELECTED FROM THE GROUP CONSISTING OF (1) A GLYCOL OF 2 TO 4 CARBON ATOMS, (2) GLYCERIN, AND (3) 1-OCTANOL, AND MIXTURES THEREOF, EFFECTING SATURATION OF THE VEHICLE WITH RESPECT TO SAID HYDRATED PHOSPHATE BY AGITATING THE SUSPENSION, AND REMOVING WATER VAPOR FROM THE SUSPENSION WHILE MAINTAINING THE TEMPERATURE OF THE SUSPENSION WITHIN THE RANGE OF ABOUT 70*F. TO ABOUT 180*F., WHEREBY SUCCESSIVE PORTIONS OF SAID HYDRATED PHOSPHATE ARE DISSOLVED, RENDERED INSOLUBLE IN THE VEHICLE BY REMOVAL OF THE WATER OF CRYSTALLIZATION OF THE PHOSPHATE AND PRECIPITATED AS COLLOIDAL PARTICLES, WITHOUT SUBSTANTIAL DECOMPOSITION AND LOSS OF THE CHEMICAL IDENTITY OF THE BASIC PHOSPHATE. 